Variable mass oscillation exciter

ABSTRACT

An oscillation exciter, for use for example in vibratory ground rollers, comprises at least one rotatably mounted container, such as a cylinder, having a driving mechanism by which it can be rotated and having its interior divided into two chambers. Means such as a pump and control valve are provided for selectively injecting and venting hydraulic liquid into and from both the chambers to cause the container and the liquid which it contains to form an unbalanced mass, the magnitude of which can be varied in dependence upon the volume of liquid in each of the chambers. Preferably the container is divided into its two compartments by a movable partition in the form of a reciprocating piston or a rotary vane-piston.

United States Patent Vural VARIABLE MASS OSCILLATION EXCITER GulertanVural, Emmelshausen, Germany Inventor:

Koehring GmbH Bomag Division, Boppard; Rhine, Germany Filed: July 19,1974 Appl. No.: 489,896

Assignee:

Foreign Application Priority Data July 25, 1973 Germany 2337695References Cited UNITED STATES PATENTS Carrier Brandt .1

Clements Kaltenegger 404/1 17 1 June 10, 1975 3,606,796 6/1969 Pappers74/87 3,616,730 11/1971 Boone et a1 404/117 3,656,419 4/1972 Boone404/117 3,813,950 6/1974 Ebersole 74/87 Primary ExaminerMervin SteinAssistant Examiner-Steven Hawkins Attorney, Agent, or Firm-Spencer 84Kaye 5 7 ABSTRACT An oscillation exciter, for use for example invibratory ground rollers, comprises at least one rotatably mountedcontainer, such as a cylinder, having a driving mechanism by which itcan be rotated and having its interior divided into two chambers. Meanssuch as a pump and control valve are provided for selectively injectingand venting hydraulic liquid into and from both the chambers to causethe container and the liquid which it contains to form an unbalancedmass, the magnitude of which can be varied in dependence upon the volumeof liquid in each of the chambers. Preferably the container is dividedinto its two compartments by a movable partition in the form of areciprocating piston or a rotary vane-piston.

14 Claims, 6 Drawing Figures PATENTEDJUM 10 I975 SHEET FIG. 1

FIG. 2

PATENTEDJUH 10 ms 3,888,600

SHEET 'IIIIIIIIIIIIIIIIZ PATENTEDJUH 10 ms 3 8 a P 6O 0 SHEET 3 FIG. 6

VARIABLE MASS OSCILLATION EXCITER BACKGROUND OF THE INVENTION Thisinvention relates to oscillation exciters for use for example invibratory ground rollers and of the kind comprising at least onerotatably mounted container, the interior of which is divided into twochambers, means for rotating the container and means for selectivelyinjecting and venting liquid into one of the compartments to cause thecontainer and liquid contained in it to form an unbalanced mass.

In one oscillation exciter of this kind, a container in the form of acylinder contains both hydraulic fluid and a spring-loaded piston whichdivides the cylinder into its two compartments. The hydraulic fluid isinjected into the cylinder against the action of the spring, which is onthe opposite side of the piston from the fluid and thus alters theposition of the piston in the cylinder. A problem arises if it isdesired to adjust the unbalanced mass to suit changes in the speed ofrotation of the cylinder, in that the spring thrust must counteract theunbalanced mass of the liquid and piston. The spring is however capableof providing the necessary counterthrust only to a limited extent.Furthermore the hydraulic fluid tends to leak past the piston into thecylinder chamber containing the spring and consequently after a periodof operation it becomes difficult to adjust the unbalanced massaccurately.

SUMMARY OF THE INVENTION The aim of the present invention is to providean inproved oscillation exciter of the kind described above.

To this end, according to this invention, an oscilla tion excitercomprises at least one rotatably mounted container the interior of whichis divided into two chambers, means for rotating the container and meansfor selectively injecting and venting liquid into and from both thechambers to cause the container and liquid contained in its chambers toform an unbalanced mass.

When the container is in the form of a cylinder divided into twochambers by a piston, the cylinder is entirely filled with hydraulicfluid.

The liquid injected into the other chamber of the cylinder then fulfilsthe function of the spring in the form of oscillation exciter describedabove. After hydraulic lines through which the liquid is injected andvented have been closed the liquid which fills the second chambercounteracts the thrust applied to the piston by the liquid in the firstchamber. Furthermore any liquid leaking from one chamber into the otherdoes not give rise to difficulties.

On the other hand, when the container is divided by a fixed wall, thecontainer need not be entirely filled with hydraulic fluid. In thiscase, when the container is a cylinder which is rotated about itslongitudinal axis the chambers are disposed one on each side of the axisof rotation and the liquid can conveniently be distributed between thetwo chambers so as to adjust the out of balance mass and thus theexciting force of the oscillation independently of the speed of rotationof the container. For example the exciting force can be kept constant asthe speed of rotation varies. To keep the exciting force constant thequantities of liquid in the two chambers are made more nearly equal toeach other as the speed of rotation increases and are conversely mademore unequal as the speed decreases. The changing of the quantities ofliquid in the two chambers can be effected by injecting more liquid intoone of them, or by venting liquid from the other, or both. In the lattercase, the quantities of liquid in the two chambers can be altered bypumping liquid from one chamber into the other.

To vent liquid from one chamber it is merely necessary to open an outletvalve, whereupon liquid is expelled from the chamber by centrifugallygenerated pressure, the liquid escaping radially outwardly. Liquid canbe injected into the chamber through an inlet duct near the axis ofrotation. The several techniques for changing the quantities of liquidin the chambers can if desired be combined.

A container in the form of a cylinder which is mounted to rotate aboutan axis coaxial with its longitudinal axis may contain a rotaryvanepiston which is acted upon by hydraulic fluid in a manner analgous tothat described above for an axially sliding piston. The rotary-vanepiston forms an unbalanced mass and cooperates with a second unbalancedmass, preferably in the form of a stationary vane. in such a way thatthe exciting force, which excites the oscillation, can be varied or heldconstant by rotating the rotary-vane piston.

In one example of the invention, the two chambers of the container areconnected together through a hydraulic line containing a pump whichforms the means for injecting the liquid into the chambers. The pump maybe mounted to rotate in common with the container. It is therefore notnecessary to provide a rotary seal between the pump and the container. Aseal of this kind is very difficult to engineer and consequently oftengives trouble in operation.

Further advantages are obtained by using a rotary pump such as agear-pump. This makes it possible to use a rotating pump housing and apump shaft which is held stationary. It is therefore not necessary toprovide a separate drive for the pump. As the container rotates, thepump housing also rotates and the pump shaft remains stationary to drivethe pump.

The injection of liquid into the chambers is preferably controlled by acontrol valve of the sliding shuttle type installed in the delivery linebetween the pump and the container. When the injection of liquid hasbeen completed, to make an adjustment of the exciting force, the controlvalve may connect the pump discharge to a reservoir for the liquid withthe result that the pump circulates the liquid from and back into thereservoir. This arrangement is structurally advantageous in those caseswhere the reservoir is formed by a rotary hollow shaft on which thecontainer. the pump and the control valve are mounted.

BRIEF DESCRIPTION OF THE DRAWINGS Three examples of oscillation excitersconstructed in accordance with the invention are illustrateddiagrammatically in the accompanying drawings in which:

FIG. 1 is a diagrammatic sectional view of one example shown mounted ina rolling drum of a vibratory ground roller;

FIG. 2 is a diagram showing part of the example shown in FIG. I, but toa larger scale;

FIG. 3 is a diagrammatic cross-section of part of a second example;

FIG. 4 is a diagrammatic axial section of the part of the second exampleshown in FIG. 3;

FIG. 5 is a diagrammatic axial section through part of a third example;and

FIG. 6 is a hydraulic circuit diagram showing part of a hydrauliccircuit of the third example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a section through aground-compacting drum of a vibratory ground roller having two paralleldrums, one behind the other. The roller drum has a tire mounted on twoend-walls 14, each of which has a central opening containing aroller-bearing housing 9, which has two functions. Each roller-bearinghousing 9 supports a roller bearing 8 for a hollow rotary shaft 1 andalso a roller bearing 10 on which the roller drum rotates in a machineframe 11 of the vibratory ground roller. The hollow rotary shaft Isupports two cylinders 3 spaced equally from the end-walls l4 andsituated in the same axial plane through the hollow rotary shaft 1. Eachcylinder 3 contains a piston 2. Hydraulic fluid is fed to the cylinders3 under pressure by a gear-pump 4 through hydraulic lines 13 and 12 sothat hydraulic fluid under pressure can be applied to both the faces ofboth the pistons 2. The hollow rotary shaft 1 has endwalls allowing itto act as a reservoir for containing hydraulic fluid. The gear-pump 4sucks hydraulic fluid out of the hollow roatary shaft 1. For controllingthe flow and pressure of the hydraulic fluid applied to the faces ofeach of the two pistons 2, the hydraulic line 13 contains a controlvalve 5. The housing of the pump 4 is fixed to the hollow rotary shaft1, and the pump is driven by the rotation of the shaft. A pump spindle 7which is coupled to the pump through a coupling 6, is connectedmechanically either to the roller-bearing housing 9 or to the machineframe 11 of the vibratory ground roller. The pump is therefore driven bythe relative rotation between the hollow rotary shaft 1 and theroller-bearing housing 9 or the machine frame 11.

The cylinders 3 which rotate with the hollow rotary shaft 1, excite theroller drum into oscillation due to the fact that the piston 2 formunbalanced masses. The exciting force producing oscillation iscontrolled by adjusting the positions of the pistons 2, by means of thehydraulic control valve 5 by admitting hydraulic fluid to the cylinderon one side of each piston and venting it from the other side. As shownin FIG. 2, the valve 5 has a spring-loaded shuttle 52 which slides backand forth in a valve housing 51. The shuttle 52 is thrust axially inopposite directions by two compression springs 53, one at each end. Thespring thrust is adjusted by the operator of the machine, preferablyelectromechanically by remote control, by means of a spring end-support54 which can be adjusted in position axially, for example by means of ascrew-threadv When, for example, the operator advances the end-support54 inward this increases the thrust applied by the one spring to thepiston valve, with the result that the piston valve slides axially untilthe two springs apply equal thrusts. Thus every change in the axialposition of the end-support 54 produces a new and different position ofequlilbrium of the shuttle 52 in the valve housing 51.

In the example illustrated, inward movement of the end-support 54, whichincreases the two spring thrusts, shifts the piston valve 52 in such away that a radially outer cylinder chamber A is vented to the liquidreservoir and the pump 4 pumps hydraulic fluid from the liquid reservoirto the radially inward cylinder chamber B.

On the other hand, outward movement of the endsupport 54, which reducesthe two spring thrusts, shifts the piston-valve 52 in the oppositedirection so that the radially inward cylinder chamber B is vented tothe liquid reservoir and the pump now supplies hydraulic fluid to theradially outward cylinder chambc- A.

When the pump is delivering fluid to cylinder chamber B, at the sametime expelling fluid from the cylinder chamber A to theliquid-container, the resulting radi ally outward movement of the piston2 is retarded by a throttling valve 55. since the fluid expelled fromthe cylinder chamber A passes through the throttling valve 55 on its wayto the liquid reservoir. Similarly, when the pump is delivering fluid tothe cylinder chamber A, at the same time expelling fluid from thecylinder chamber B, the inward movement of the piston 2 is retardedbecause the liquid being expelled from the cylinder chamber B passesthrough the throttling valve 55. Outward movement of the piston 2increases the exciting force producing-oscillation. and inward movementdecreases it. The hydraulic lines 12 are balancing lines connecting thecylinder chambers A of the two cylinders 3 together and the cylinderchambers B together, ensuring that the two pistons 2 in the twocylinders 3 move synchronously.

After each piston movement the end-support 54 is returned to itsposition of rest and the shuttle 52 also returns to its position of restin which it closes the hydraulic lines and locks the pistons 2 inposition. When the valve 5 is closed, the pump 4 circulates thehydraulic fluid from and back to the reservoir formed by the shaft 1.For example, the pump can simply vent the fluid out through apressure-release valve into the reservoir, or the pump can deliver thefluid to the reservoir through the valve 5 and through a hydraulic line.Connections between the cylinder chambers A and B, the gear-pump 4 andthe reservoir are arranged as follows. The two connections for thecylinder chambers A and B are positioned in the valve housing 5],equally spaced at pre-determined axial distances on each side of theconnection of the pump. The two connections for the hydraulic linesleading through the throttling valve 55 to the reservoir are alsosituated equally spaced on each side of the connection for the gearpump4, but farther away from it. The shuttle 52 has two peripheral groovesor the like, of axial lengths greater than the distances betweenadjacent connections, the peripheral grooves being spaced closertogether than the adjacent connections. The peripheral grooves arepositioned so that when the shuttle 52 is in its position of rest theconnections to the cylinder chambers A and B are each in the middle of agroove.

Instead of the arrangement shown in FIGS, 1 and 2, with cylinders 3 theaxes of which are radial with respect to the hollow rotary shaft 1, eachcylinder containing a piston 2, the arrangement shown in FIGS. 3 and 4can be used. This example of the invention has a cylinder 30 surroundingthe hollow rotary shaft 1 coaxially. The cylinder 30 contains arotary-vane piston 20 which rotates on the hollow rotary shaft 1. The totary-vane piston 20 can if desired be connected to the cylinder 30through a torsion spring. The rotary vane provided by piston 20 is fixedto a bushing which is rotatably mounted on the hollow rotary shaft 1.The vane piston projects radially outwardly from the bushing and itsouter end slides over the inner suface of the cylinder 30. A stationaryvane projects radially inwardly from the inner surface of the cylinder30 and its inner end slides on the outer surface of the bushv The twovanes between them form cylinder chambers A and B.

When the two vanes are diametrically opposite each other, as shown inFIG. 3, their masses exactly counterbalance each other and there isconsequently no unbalanced mass. Hydraulic fluid delivered to one of thecylinder chambers A or B and vented from the other rotates the rotaryvane, in one direction or the other, towards the stationary vane, withthe result that the two vanes together now form an unbalanced mass. Thegreatest unbalanced mass is obtained when the two vanes are side by sidein contact with each other. The arrangement makes it easy to adjust theexciting force to suit the speed of rotation of the hollow rotary shaft,if desired so as to keep the exciting force constant with variations inthe speed of rotation. To obtain this effect the rotary vane is rotatedaway from the stationary vane as the speed of rotation increases andtowards it as the speed decreases.

Hydraulic fluid is supplied to the chambers A and B by a pump 21 throughhydraulic lines 22 and 23, and through other lines which are not shownin the drawings forming a circuit which includes a control valve 24which is housed inside the hollow rotary shaft 1 together with the pump21. The control valve 24 is actuated by a control spindle 25 which ismounted, coaxially with the hollow rotary shaft 1, inside a hollow spindle 26 which drives the pump through a gear train 28. The hollow spindle26 rotates in hearings in a connecting piece 27 mounted inside thehollow rotary shaft 1. The gear train consists of a pinion which isfixed to the hollow spindle 26 and meshes with a second pinion fixed tothe drawing shaft of the pump. Rotation of the hollow spindle 26relative to the hollow rotary shaft 1 drives the pump. When the pump isin operation it delivers hydraulic fluid through the control valve 24,the fluid either flowing through the lines 22 and 23, to one or theother of the two cylinder chambers, or returning to the hollow rotaryshaft 1, which acts as a liquid reservoir. It will be observed that thepump 21 can be constructed simply as a pressure pump. The liquid in thehollow rotary shaft 1 flows easily into the pump 21, because the inletof the pump is situated close to the inner surface of the hollow shaft.As the hollow shaft 1 rotates the liquid distributes itself evenly overthe inner surface of the hollow shaft and is driven into the pump 21through its inlet opening by centrifugal force.

The hydraulic fluid used for moving the pistons 2 or in the two examplesis oil which also functions as a lubricant. The pump 4 or 21 can forexample also be used to pump the oil to lubrication points on themachine through a hydraulic line leading from the pressure line throughwhich the pump 4 or 21 delivers oil to the control valve 5.

In the example shown in FIGS. 5 and 6 a hydraulic fluid container whichin this cause is formed by the hollow rotary shaft 1 is divided by awall 31 extending parallel to the longitudinal axis of the shaft, so asto form the two chambers A and B, which are connected together through ahydraulic line 32 and a suction and pressure pump 33. A driving shaftfor the pump is coax ial with the hollow rotary shaft 1 and drivesthrough an electric coupling 35 and through a flexible coupling 34, sothat the driving shaft can be accelerated or braked relative to thehollow rotary shaft 1. The pump 33 is provided with a control valve 36.The system allows hydraulic fluid to be pumped as desired between thetwo cylinder chambers A and B, making it possible, for example, to holdthe exciting force of the oscillation exciter constant irrespective ofvariations in the speed of rotation of the hollow rotary shaft 1. Theelectric coupling 35 can. for example, be actuated through a time relay,the coupling 35 being engaged for a period which depends on the pumpoutput and the change in shaft speed, so that the desired quantity ofhydraulic fluid is transferred from the one cylinder chamber to theother. in order to obtain the desired change in the exciting force.

1 claim:

1. An oscillation exciter comprising at least one cylinder, meansrotatably mounting said cylinder. means for rotating said cylinder, apiston movably mounted in said cylinder for dividing said cylinder intotwo chambers, and means for selectively injecting and venting liquidinto and from both said chambers to move said piston so as to cause saidpiston and the liquid contained in said chambers to form an unbalancedmass.

2. An oscillation exciter as claimed in claim 1, wherein said cylinderis oriented so that its longitudinal axis is transverse to the axis ofits rotation and said pis ton is mounted for sliding movement in thedirection of the longitudinal axis of said cylinder.

3. An oscillation exciter as claimed in claim 1, wherein said rotatablemounting means mounts said cylinder for rotation about an axis coaxialwith the iongitudinal axis of said cylinder, and said piston is arotary-vane piston.

4. An oscillation exciter as claimed in claim 1, further comprisinghydraulic duct means connected to said chambers, and wherein saidinjecting means comprise a pump connected into said hydraulic ductmeans.

5. An oscillation exciter as defined in claim 4 wherein said pump is arotary pump.

6. An oscillation exciter as defined in claim 1 further comprising meansdefining a reservoir mounted for rotation with said cylinder.

7. An oscillation exciter as claimed in claim 4, further comprising areservoir, hydraulic duct means between said cylinder, said reservoirand said pump, and control valve means operatively connected in saidhydraulic duct means, said control valve means being operative toselectively connect said pump to one of said chambers to inject liquidinto said one chamber, and the other of said chambers to said reservoirto vent said other chamber.

8. An oscillation exciter as claimed in claim 7, further comprising ahollow rotary shaft forming said reservoir and means mounting saidcylinder, said pump and said control valve means on said hollow rotaryshaft.

9. An oscillation exciter as claimed in claim 7, wherein said meansdividing said cylinder into two chambers is a rotary-vane piston, andfurther comprising means mounting said rotary-vane piston on said hollowrotary shaft and means fixing said cylinder to said shaft.

10. An oscillation exciter as claimed in claim 1 wherein there are twoof said cylinders mounted on said mounting means, and further comprisingduct means connecting each chamber of one of said cylinders to arespective chamber of the other of said cylinders.

11. An oscillation exciter comprising at least one container, meansrotatably mounting said container,

means for rotating said container, means dividing said container intotwo chambers, and means including a pump for selectively injectingliquid into and venting liquid from both said chambers to cause saidcontainer and liquid contained therein to form an unbalanced mass. saidpump including a part operatively coupled to said container for rotationtherewith and a stationary part, relative rotation of said partsoperating said pump.

12. An oscillation exciter as claimed in claim ll, wherein said pump isa rotary positive displacement pump.

13. An oscillation exciter as claimed in claim ll, wherein said pumpincludes a housing and a shaft, said 8 housing forming said partoperatively coupled to said container and said shaft forming saidstationary part.

14. In a ground-compacting vibratory roller including a rolling drum andan oscillation exciter for vibrating said drum, the improvement whereinsaid oscillation exciter comprises at least one cylinder, meansrotatably mounting said cylinder, means for rotating said cylindcr, apiston movably mounted in said cylinder for dividing said cylinder, intotwo chambers, and means for selectively injecting and venting liquidinto and from both said chambers to move said piston so as to cause saidpiston and liquid contained in said chambers to form an unbalanced mass.

1. An oscillation exciter comprising at least one cylinder, meansrotatably mounting said cylinder, means for rotating said cylinder, apiston movably mounted in said cylinder for dividing said cylinder intotwo chambers, and means for selectively injecting and venting liquidinto and from both said chambers to move said piston so as to cause saidpiston and the liquid contained in said chambers to form an unbalancedmass.
 2. An oscillation exciter as claimed in claim 1, wherein saidcylinder is oriented so that its longitudinal axis is transverse to theaxis of its rotation and said piston is mounted for sliding movement inthe direction of the longitudinal axis of said cylinder.
 3. Anoscillation exciter as claimed in claim 1, wherein said rotatablemounting means mounts said cylinder for rotation about an axis coaxialwith the longitudinal axis of said cylinder, and said piston is arotary-vane piston.
 4. An oscillation exciter as claimed in claim 1,further comprising hydraulic duct means connected to said chambers, andwherein said injecting means comprise a pump connected into saidhydraulic duct means.
 5. An oscillation exciter as defined in claim 4wherein said pump is a rotary pump.
 6. An oscillation exciter as definedin claim 1 further comprising means defining a reservoir mounted forrotation with said cylinder.
 7. An oscillation exciter as claimed inclaim 4, further comprising a reservoir, hydraulic duct means betweensaid cylinder, said reservoir and said pump, and control valve meansoperatively connected in said hydraulic duct means, said control valvemeans being operative to selectively connect said pump to one of saidchambers to inject liquid into said one chamber, and the other of saidchambers to said reservoir to vent said other chamber.
 8. An oscillationexciter as claimed in claim 7, further comprising a hollow rotary shaftforming said reservoir and means mounting said cylinder, said pump andsaid control valve means on said hollow rotary shaft.
 9. An oscillationexciter as claimed in claim 7, wherein said means dividing said cylinderinto two chambers is a rotary-vane piston, and further comprising meansmounting said rotary-vane piston on said hollow rotary shaft and meansfixing said cylinder to said shaft.
 10. An oscillation exciter asclaimed in claim 1 wherein there are two of said cylinders mounted onsaid mounting means, and further comprising duct means connecting eachchamber of one of said cylinders to a respective chamber of the other ofsaid cylinders.
 11. An oscillation exciter comprising at least onecontainer, means rotatably mounting said container, means for rotatingsaid container, means dividing said container into two chambers, andmeans including a pump for selectively injecting liquid into and ventingliquid from both said chambers to cause said container and liquidcontained therein to form an unbalanced mass, said pump including a partoperatively coupled to said container for rotation therewith and astationary part, relative rotation of said parts operating said pump.12. An oscillation exciter as claimed in claim 11, wherein said pump isa rotary positive displacement pump.
 13. An oscillation exciter asclaimed in claim 11, wherein said pump includes a housing and a shaft,said housing forming said part operatively coupled to said container andsaid shaft forming said stationary part.
 14. In a ground-compactingvibratory roller including a rolling drum and an oscillation exciter forvibrating said drum, the improvement wherein said oscillation excitercomprises at least one cylinder, means rotatably mounting said cylinder,means for rotating said cylinder, a piston movably mounted in saidcylinder for dividing said cylinder, into two chambers, and means forselectively injecting and venting liquid into and from both saidchambers to move said piston so as to cause said piston and liquidcontained in said chambers to form an unbalanced mass.